The present invention relates to metering, that is to say, sampling and releasing a predetermined or controlled quantity of a liquid or fluid. More precisely, the invention concerns metering microvolumes of a liquid, that is to say, sampling and releasing of microquantities, for example, volumes of the order of a few microliters or of a few fractions of a microliter of a liquid.
The invention finds application, in particular, for obtaining controlled and infinitesimal dilutions, for example nanomolar dilutions.
There is currently no way of truly metering microquantities of a liquid under suitable conditions of precision, repeatability and reliability. For this purpose, pipettes or micropipettes are generally used, for example pipettes marketed by the company GILSON under the brand name GILSON 90403 P1000, which sample a predetermined volume of liquid by applying a reduced pressure which is calibrated by the course of a plunger, and release the volume sampled by applying an overpressure above the plunger.
Such a micropipette is, for example, described in document DE-A-1,598,629.
The precision of micropipettes is limited by the surface tension of the liquid sampled, the capillary forces exerted inside and outside the wall of the pipette, and attachment or retention of microdroplets on the end of the pipette.